The present invention relates to an inspection unit which is used for inspecting an electronic component to be inspected such as a semiconductor integrated circuit, and more particularly, relates to a connecting structure between a contact probe for ground and a metal block in the inspection unit having the contact probe for ground.
FIG. 12A is a sectional front view of a related-art inspection unit which forms a socket for high frequency, showing a region for mounting a contact probe for ground, and FIG. 12B is a sectional front view of a ground tube in the related-art inspection unit for interconnecting the contact probe for ground and a metal block. In FIG. 12A, a contact probe 1 for ground is an electrically conductive body having an electrically conductive tube 2 in a cylindrical shape, and electrically conductive plungers 3, 4 which are urged so as to protrude from the electrically conductive tube 2 by a spring which is incorporated therein. The contact probe 1 for ground is so arranged as to pass through a through hole 11 in a metal block (pin block) 10. Moreover, the contact probe 1 for ground is coaxially held with respect to an inner peripheral face of the through hole 11 by retainers (insulating fixing means) 12, 13 which are fixed to upper and lower faces of the metal block 10.
Interconnection between the contact probe 1 for ground and the metal block 10 is conducted using a ground tube 20 in FIG. 12B. The ground tube 20 is formed by rounding a sheet metal into a tubular shape. One end of the ground tube 20 is rounded so as to have a slightly smaller inner diameter than an outer diameter of the contact probe 1 for ground so that it can get in contact with an outer peripheral face of the probe 1, while the other end is enlarged in diameter so that it can get in contact with an inner peripheral face of the through hole 11. This ground tube 20 is disposed in a gap between the probe 1 and the metal block 10 thereby to establish electrical connection between them.
The related art as shown in FIG. 12A and FIG. 12B is disclosed as a related-art example, in JP-A-2010-60527.
By the way, the ground tube 20 in FIGS. 12A and 12B has such a shape that one side of the sheet metal is rounded to have a diameter capable of getting in contact with the contact probe 1 for ground, while the other side is enlarged so as to get in contact with an inner wall of the through hole in the metal block 10. The ground tube 20 is caused to be in contact with the metal block 10 and the contact probe 1, utilizing elasticity of the ground tube 20 which is enlarged, thereby to establish the electrical connection. For this reason, there are several problems which are listed below.
(1) Because the ground tube 20 is formed by folding a stamped metal sheet by hand into a trumpet shape, it is difficult to secure accuracy in size. Moreover, because the ground tube 20 is formed by hand, a manufacturing cost is high.
(2) Because the ground tube 20 is formed by hand, there is a large dispersion in diameter, and so, a problem of bad assembling performance occurs, as described below.
a. Because an edge of a small diameter part of the ground tube 20 bites into the contact probe 1, the contact probe 1 cannot be re-used, in some cases.
b. Because an edge of a large diameter part of the ground tube 20 bites into the inner face of the through hole in the metal block 10, it becomes difficult to remove the ground tube 20.
c. Movement of the contact probe 1 is restricted inside the metal block 10 by the ground tube 20 which is curved (and this causes a situation where the contact probe 1 can be inserted up to halfway only), and so, it is difficult to assemble the retainers 12, 13, in some cases.